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Among the complex melody of molecules that create a wine's bouquet is another chemical signature - the consumption of fossil fuels.

Researchers from the Netherlands are investigating whether levels of fossil-fuel-derived carbon dioxide measured in the wine's alcohol could help track CO2 emissions in a given region.

They hope this may help determine which carbon-management schemes work best and refine regional models of climate change.

"It's going to become more and more important to develop these techniques to measure carbon dioxide from fossil fuels in surface air so we can diagnose regional fossil fuel emission reductions," says Associate Professor Jim Randerson of the University of California, Irvine, who was not a part of the study. "This could be a really valuable component of a new network."

The approach offers an alternative to stations that measure CO2 directly, which are relatively scarce.

"There are less than 10 measurement stations in the whole of Europe," says the study's lead author, Sanne Palstra of the Center of Isotope Research at the University of Groningen in the Netherlands.

"If we want to say more about spatial and temporal variations in Europe, we have to increase the number of sites."

Telltale sign

The approach measures the amount of the radioactive isotope of carbon, carbon-14, which is created by cosmic rays high in the atmosphere, and by nuclear explosions, which were a significant source in the mid-twentieth century.

This isotope represents a small proportion of the carbon atoms in the CO2 in the atmosphere, and is taken up by plants as they grow.

Over time, carbon-14 decays into the isotope nitrogen-14. Fossil fuels, made from plant material that lived hundreds of millions of years in the past, have virtually no carbon-14.

When fossil fuels are burned, the resulting CO2 is nearly carbon-14-free. So air with less carbon-14 in its CO2 carries higher amounts of fossil-fuel-derived carbon.

This signature is carried through the plants as they use the CO2 to grow throughout the season - and into the wine made from that year's grapes.

Palstra and colleagues analysed wine from different regions of Europe, distilling off the ethanol and measuring the amount of carbon-14.

Comparing vintages

They compared the amount with a reference sample from a location in the Swiss Alps, far from any local fossil fuel emissions.

"In northern Italy and in Germany, you could see there were more fossil fuel emissions," says Palstra.

"I could really see very clearly the proximity of industries or an airport. In that sense it's a quite a sensitive method."

"You can look back in the atmosphere by measuring wines," adds Palstra, by analysing the vintages of different years.

Palstra found that there was significant variation in a given location from year to year, which may represent effects from weather patterns. It will be important to include weather information in calculating the amount of fossil fuel CO2 in the future, she adds.

Measurements of wine ethanol would be limited to wine-growing regions, but other plant material could be used as well.

Randerson was part of a study that used the leaves of corn plants in the United States to look at the amount of fossil fuel carbon in different regions.

"The European scientists know how to conduct their science in style," Randerson concedes. "Here in the US, we do it with corn. In Europe, they use wine."